Vacuum condensed silver halide layers of increased sensitivity



Feb. 13, 1968 R. MATEJEC ET AL 3,368,895

VACUUM CONDENSED SILVER HALIDE LAYERS OF INCREASED SENSITIVITY Filed Aug. 26, 1963 United States Patent Ofiice 3,368,895 Patented Feb. 13, 1968 7 Claims. (61. 96-28) The present invention relates to photo-sensitive silver halide layers which are produced by vapor condensation under vacuum of silver halide on bands, strips or sheets of appropriate base material.

The production of photosensitive silver halide layers free from binding agents by depositing evaporated silver halide onto a carrier in vacuo is disclosed in French Patent 1,267,623 and in German Patent 938,644. In the process according to US. Patent 2,945,771, similar materials are obtained by halogenating silver layers that have been produced by vapor condensation under vacuurn. Owing to the ease and speed with which they can be produced, photosensitive layers produced by the above process are superior, particularly for continuous work, to the conventional materials which are produced by applying an aqueous gelatine emulsion of silver halide on to the carrier and which require a relatively time-consuming drying process. Hitherto, the use of silver halide evaporation layers has been prevented by their inferior photosensitivity.

In principle, the usual sensitizing processes for photographic emulsions could be used for increasing the photosensitivity of these evaporation layers. These sensitizing processes generally consist of the so-called chemical ripening of the layers by using special types of gelatine which contain ripening compounds or by adding special chemical sensitizers such as sulphur compounds or compounds of noble metals in an aqueous gelatine solution. The use of these methods, however, would cancel out the above described advantages of the vacuum condensed layers because it would require treatment with aqueous solutions.

We have now found that the sensitivity of vacuum condensed silver halide layers can be increased very considerably by means of new sensitizers so that light-sensitive layers can be obtained which are comparable in their light-sensitivity to conventional silver halide emulsion layers. These sensitizers can be divided into the following two groups:

The first group includes thiocyanates and halides such as chlorides, bromides and iodides of oxidizable metallic cations such as cations of the following metals: Cu+, Au Pt, Pd+ Rh+, Fe, Ni, Co+ Hg Sn, Pb Among these compounds halides of Cu+ and Fe, preferably CuCl, CuBr, FeCl FeBr have proved to be especially effective.

These sensitizers mainly increase the sensitivity of the vacuum condensed silver halide layers to high intensity exposure, for instance, to exposure by means of a highpressure mercury-arc lamp, the radiation of which contains a high proportion of blue and ultraviolet light.

The sensitizers are incorporated inside the silver halide by simultaneous evaporation and condensation of silver halide and of the sensitizer. For producing these layers the sensitizers may be mixed with the silver halide before evaporation or the silver halide and the sensitizer may be simultaneously evaporated from separate sources and simultanousely condensed on the same support. The sensitizers may be used in concentrations of 10 to 20, preferably 10 to 10 mol percent calculated on the silver halide.

The second group of the new sensitizers for vacuum condensed silver halide layers includes metals and their oxides, sulphides, selenides or tellurides, particularly those of Groups Ib, IIb and VIII of the Periodic System of elements, e.g., Cu, Ag, Au, Pt, Pd, Rh, Hg or Cd.

These sensitizers may be applied in order to sensitize the surface of vacuum condensed silver halide layers. In this case they increase particularly the sensitivity to low intensity exposure such as by an incandescent lamp. To produce such material, a silver halide layer of a thickness of 1 to microns, preferably 5 to 20 microns, containing no additive or merely the sensitizers of the first class is deposited by vacuum condensations on a suitable support and a much thinner silver halide layer containing the last mentioned sensitizers is deposited on the first layer, again by vacuum evaporation and condensation. This outer silver halide layer has a thickness of about 0.01 to 1 micron, preferably about 0.01 to 0.1 micron and its silver halide composition may he the same as or different from that of the first layer. The proportion of silver halide to sensitizing agent in said layer may be the same as in the first layer.

Silver halide layers of particularly high general sensitivity can be obtained by using both of the above described groups of sensitizers. However, in particular cases it is possible to sensitize the layers specifically to high intensity exposure or to low intensity exposure by using substances from only one of these groups.

In order to obtain reproducible conditions in which to effect the sensitization according to the invention, it is advisable to produce the photosensitive layers from silver halide which has been purified by monocrystal growing (compare A. Neuhaus, Chemie Ingenieur Technik, 28 (-6) 155, 350) or by the zone melting process (compare F. Moser et al. in J. Appl. Phys, 32 (1961) 48, and P. J. Schlichte in J. Sci. Instium, 39 (1962) 392. As already described above, the sensitizing additives may be deposited by vacuum evaporation and condensation on to the support simultaneously with the silver halide but from a separate site of evaporation. However, it is advantageous to incorporate the additives in the purified silver halide before evaporation, for instance, by mixing the components before evaporation and melting them under exclusion of air either under an atmosphere of a protective gas such as nitrogen or a rare gas, or under vacuum.

The sensitization according to the invention can be obtained both with layers which consist of a uniform silver halide such as silver chloride, silver bromide or silver iodide and with layers which consist of a mixture of silver halides. Preferred are layers, the silver halides of which consist of silver chloride or silver bromide.

It is advisable to improve the adhesion of the silver halide on its support by applying adhesive layers, again by vacuum evaporation and condensation. These adhesive layers may be composed of oxidic or metallic substances such as tin oxides or silicon oxide or titanium oxide or silver; they should have a thickness of about 0.5 micron.

Suitable supports for the silver halide layers are the usual film-forming synthetic resins such as polycarbonates, cellulose esters, polystyrene, polyvinyl chloride, polyesters, particularly those of terephthalic acid and glycols, and paper. The thickness of the carrier is immaterial but is approximately 50 to 200 microns.

After imagewise exposure the light-sensitive layers of the present invention may be developed in a silver halide developer solution which is not capable of dissolving silver halide, that is to say which is devoid of silver halide solvents such as sulfites, thiosulfates and thiocyanates.

3 Examples of suitable developer solutions are:

p-Hydroxy phenyl glycme grams 3 Potassium carbonate do Potassium bromide do 0.1 Water liter 1 Ascorbic acid "grams" 3 1-phenyl3-pyrazolidone do 0.5 Ethylene-(iiarnin-tetraacetic-Na+ salt do 8 Potassium bromide do 0.1 Water liter 1 Example I An adhesive layer about 0.1 micron in thickness and composed of (SiO+SiO is first deposited by evaporation in vacuo onto a polycarbonate foil of about 0.1 mm. thickness.

A photosensitive silver halide layer, about 10 microns in thickness and containing 95% by weight of AgBr, 4% by weight of Agl, 0.5% by weight of CuCl and 0.5% by weight of FeCl;; is then deposited on this adhesive layer by vacuum evaporation and condensation by methods known as such (compare for instance French Patent 1,267,623). The AgBr and Agl had been purified by the zone melting process prior to being deposited by evaporation (compare the chapter, Techniques of Zone Melting and Crystal Growing, by W. G. Pfann in Solid State Physics volume 4, Academic Press Inc, publishers, New York 1957).

A mixture of 98.5% by weight AgBr, 1% by Weight of Ag Ct and 0.5% by weight of Au is then deposited by evapo a'tion as surface sensitizer on the silver halide layer so obtained. The Ag O and Au are mixed in a finely pulverized form with the AgBr melt prior to evaporation. This surface layer has a thickness less than 0.1 micron.

Alter imagewise exposure by means of incandescent light the material is developed in one of the above developer solutions. The speed of the material is 10 times as high as a material which has been produced in the same manner as the above material but without incorporation of the cited additives. After development the silver image is transferred to an auxiliary support by contacting the silver halide layer with a moist hydrophilic colloid layer coated on a paper support and thereafter separating the two materials.

Example 2 An adhesive layer of SnO of about 0.5 micron in thickness is deposited by evaporation in vacuo on a foil of polyethyleneterephthalate of about 0.1 mm. in thickness.

A photosensitive layer containing 99.9% by weight of AgCl and 0.1% by weight or" SnCl and about 10 microns in thickness is then deposited on this adhesive layer by evaporation and condensation in vacuo. A mixture of 99% by weight of AgBr and 1% by weight of Ag S is then deposited by evaporation in vacuo on the silver halide layer so obtained. This surface layer has a thickness of 0.1 micron. The speed of the material surpasses that of a non-sensitized material by a factor of 50, when exposed and processed as in Example 1.

Example 3 An adhesive layer of SiO, about 0.5 micron in thickness, is deposited by evaporation and condensation in vacuo on a foil of acetyl-cellulose which is about 0.1 mm. in thickness. A photosensitive layer consisting of 99% by weight of AgBr or AgCl and 1% by weight of PbS, which is about 10 microns in thickness, is then deposited by evaporation and condensation in vacuo. The sensitivity of the material is times as great as that of the unsensitized material when exposed and processed as in Example 1.

Example 4 The process of Example 3 with the variation that the following components are used for the production of the light-sensitive layer.

(a) 99% by \vei ht of AgCl 1% by weight of FeCl (b) 99% by weight of AgBr 1% by weight of CuBr (c) 99% by weight of AgCl 1% by weight of CuCl (d) 99% by weight of AgBr 1% by weight of FeBr The increase in speed achieved with these layers over comparable unsensitized layers corresponds to the factor 5()l00.

According to a further feature of the present invention the silver halide layers disclosed above may be used for the production of direct positive silver images by develop ing the exposed silver halide layers to produce a negative silver image, transferring the silver image to an auxiliary support and developing the residual silver halide to pro duce a positive image.

The developers which are used for the first development of the exposed silver halide layers are described above. They should not contain a silver halide solvent. The difference in sensitivity to the action of the developer solution between the exposed and non-exposed areas of the layer may be increased either by adding restrainers or anti-fogging agents to the developer solutions or by treating the layers between exposure and development with a solution or dispersion of synthetic or natural protective colloids such as gelatine, albumin, polysaccharoses or their derivatives, polyvinylalcohol, polyvinylpyrrolidone. The same eltect is achieved by using baths containing additives which restrain or inhibit the development of the non-exposed silver halide. Suitable compounds of this type are, for instance, stabilizers for silver halide emulsions such as benzotriazole, nitrobenzimidazole, lphenyl-S-mercaptotetrazole, Z-mcrcaptobenzthiazole. These substances may also be used as additives for the first development solution.

For the second development which takes place after the transfer of the negative silver image there may be used the same developer solutions as for the first development, these solutions having added thereto fogging agents or agents increasing the speed of development as they are known in the art of developing non-exposed silver halide emulsion layers. Such additives include for instance, organic or inorganic sulfur compounds, such as sodium-sulfide, and reducing agents such as tin-lI-compounds and hydrazine.

The transfer material used for receiving the negative silver image may consist of a sheet-like film or paper support having coated thereon a layer of a hydrophilic film-forming colloid, such as gelatine, polyvinylalcohol, cellulose derivatives, polysaccharoses, which in wet condition are capable of adhering to the recited silver image.

Example 5 A silver halide material as disclosed in Example 2 is exposed to a line original by means of an incandescent lamp (100 watts) for about 30 seconds.

The exposed material is developed in a developer solution of the following composition:

Parahydroxyphenylgylcine -grarns 2.4 Sodium carbonate anhydrous do 12 Water liter 1 The developing time is 20 seconds, the temperature of the solution is 20 C. There is obtained a negative of the original. The developed film is contacted under light pressure with a gelatine layer of a transfer material, having a paper support. The gelatine layer of the transfer material may be moistened with water or with the developer solution before it is contacted with the silver halide layer.

The two materials are separated from each other. There is obtained a negative silver image which adheres to the gelatine layer of the transfer material, whereas the nonexposed areas of the light-sensitive material remain on the original support in form of a positive scarcely visible silver bromide image.

The last mentioned material is developed without previous exposures for 1 minute in the aforementioned developer solution after having added there to milliliters of an alkaline aqueous 1% solution of stannous chloride. There is obtained a positive silver image of the original which may be transferred to a transfer material in the same manner as described above.

Example 6 A silver halide material as disclosed in Example 4 is exposed for about 30 seconds to a transparent line-original by means of an incandescent lamp of 100 watts. The processing of the material is carried through in an apparatus which is illustrated in the accompanying drawing. The exposed film 1 is introduced through a slit 2 into a developing apparatus, having a housing 3. The developer solution has the following composition:

Para-hydroxyphenyl-glycine grams 0.5 Potassium carbonate do 20 Sodium carbonate do 5 Water liter 1 1-phenyl-S-mercaptotetrazole grams At the same time there is introduced in this apparatus through slit 5 the transfer material 6.

The two materials are brought into contact with each other by pressure rolls 7 and 8 whereby the negative silver image which has formed in the silver halide layer is transferred to the transfer material. The light-sensitive material is then transported through the developer liquid to the second pressure roller devices 9 and 10. During this transport the silver halide material is developed to a positive silver image of the original. The material 1 is pressed together with transfer material 6, whereby the positive silver image which has formed in the meantime is transferred to said transfer material. The transfer materials carrying the negative or the positive silver image respectively, leave the developer device through slits 11 and 1.3 respectively. The original material 1 leaves the developer device through slit 14.

A developer solution which is suitable for carrying out the above process has the following composition:

Ascorbic acid grams 0.5 l-phenyl-S-pyrrazolidone do 0.1 Borax do 10 Water liter 1 Polyvinylalcohol (protective colloid) gram 0.5

The above process has the advantage that it does not require a fixation of the exposed silver halide layer. According to another modification of the above process, the positive silver image may be left on the original support. In this case the positive silver image should be protected, by contacting it with a foil or by coating it with a lacquer solution. Furthermore there may be used a lightsensitive material which has a protective layer produced from a film-forming hydrophilic colloid, such as gelatine, polysaccharose, polyvinylalcohol or cellulose derivatives, such as carboxycellulose. In this case an uncoated transfer material having a rough surface, such as paper, may be used for the transfer of the negative and positive silver images. A suitable binding agent for such a protective layer consists, for instance, of 2 parts by weight of gelatine and 1 part by weight of carboxymethylcellulose.

The silver halide layers of the present invention which contain the first class of sensitizers may also be used as print-out materials which require no chemical development. They may be exposed to a high intensity source of radiation to form a latent image or a faintly visible image which is then developed or intensified by exposure to diffuse daylight or artificial light of lower intensity. These light-developable, direct writing layers may find utility for oscillographic recording by exposing the layers to the modulated beam of a high-pressure mercury-arc lamp (such as the Osram lamp HBO 107/1) and then developing the material by exposure to daylight or low intensity incandescent or fluorescent light.

The silver halide layers of the present invention which are used as print-out materials may have a thickness of about 0.1 to 50, preferably 0.5 to 20 microns. If at all they should contain the sensitizers of the aforementioned second group only in quantities of at most 10- percent by weight as calculated on silver halide. The sensitizers of the first group are incorporated in the layers in the same manner and in the same amounts as indicated above. For producing the layers the silver halides to be evaporated should be heated only as little as possible above their melting points, so that the formation of traces of metallic silver by thermal decomposition is avoided. The temperature of the support on which vacuum condensation of the evaporated materials takes place should be kept preferably at 5080 C. The light-sensitive layers may be provided with a protective layer, for instance, by vacuum condensing on the outer surface of the silver halide layers inorganic white pigments such as SiO TiO or A1 0 these protective layers being permeable to ultraviolet light. Moreover, the protective layers may be produced in the customary manner from organic hydrophobic or hydrophilic film forming binding agents such as gelatine, polyvinylalcohol, polyvinylpyrrolidon or polyurethanes. The support for the light-sensitive layers may be a paper or a film support. The film support may have incorporated therein white pigments such as BaSO PbSO TiO Si0 or A1 0 Furthermore, it is possible to use a transparent film support which is provided with an intermediate layer produced by vacuum condensing thereon the aforementioned pigments in order to obtain a light-reflecting surface. The light-reflecting intermediate layers may also be produced by providing a solution of a film forming col- 7 loid such as gelatine or polyvinylalcohol which solution has dispersed therein at least one of the aforementioned pigments, casting this solution on a film support and thereafter drying it.

In order to increase the sensitivity of the print-out layers, halogen acceptors may be incorporated in the film support or in the intermediate or protective layer in case that these layers are produced by a coating process. Suitable halogen acceptors are, for instance, thioureas, alde hy-des, derivatives of aldehydes such as saccharoses or polysaccharose, organic derivative of hydroxylamine and hydrazine, phenolic compounds. 7

Suitable layers for this modification of the present invention are disclosed in the following examples.

Example 7 An adhesive layer about 0.5 micron in thickness and composed of SiO+SiO in about equal parts by weight is first vacuum condensed on a polycarbonate foil of about 0.1 mm. in thickness, said foil having incorporated therein as a halogen acceptor 1 percent by weight of semicarbazide hydrochloride.

A photosensitive layer, about 10 microns in thickness and containing 99% by weight of silverchloride, 0.5% by weight of CuCl and 0.5% by weight at FeCl is then deposited on the adhesive layer by vacuum evaporation and condensation. The silver chloride which was used for the production of the above layer had been highly purified by monocrystal growing.

Example 8 An adhesive layer about 0.1 micron in thickness and composed 70% by weight of SiO and 30% by weight of SiO is produced by vacuum evaporation and condensation on a 10 microns thick foil of polyethyleneterephthalate which contains 5% by Weight of ZnO as a light reflecting pigment and by weight of calcium oxalate as a halogen acceptor. On this protection layer there is deposited by vacuum condensation a silver halide layer of about microns thickness consisting of 95% by weight of AgCl, 4.5% by weight of AgBr and 0.5% by Weight of SnCI The silver halide used in this process had been highly purified by the zone melting process. On the light-sensitive silver halide layer there is deposited by vacuum condensation a protective layer of S10 about 1 micron in thickness. The light recording obtained with the materials illustrated in the above examples are more stable than those obtained with conventional light-writing material containing a gelatino silver halide emulsion layer as light-sensitive element.

We claim:

1. A photographic material comprising a sheet-like support and a light-sensitive silver halide layer about 1 to about 100 microns thick produced by vacuum condensation on said support of a mixture of a silver halide with 10- to mol percent of a sensitizing agent selected from the halides and thiocyanates of Cu+, Au- Pt, Pd, Rh+, Fe, Ni, Co, Hg Sn and Pb and the oxides, sulphides, selenides and tellurides of metals of Groups lb, 11b, and VIII of the periodic system, said layer being protected by a transparent top coating of vacuum'condensed inert inorganic oxide pigment.

2. A support having a resin surface carrying a vacuum-condensed light-sensitive silver halide coating about 1 to 100 microns thick and mixed with 10 to 20 mol percent of a sensitizing agent selected from the halides and thiocyanates of Cu+, Au+, Pt, Pd, Rh Fe, Ni, Co, Hg+, Sn and Pb, and the oxides, sulfides, selenides and tellurides of metals of groups lb, 11b and VIII of the periodic system, the coating being adhered to the resin surface through an intervening vacuum-condensed stratum not more than about 0.5 micron thick of a bonding agent selected from the oxides from the oxides of tin, silicon, titanium and silver.

3. A photographic material comprising a sheet-like support, a first light-sensitive silver halide layer 1 to 100 microns thick produced by vacuum condensation of silver halide on said support and a second thinner, ligl1t-sensitive silver halide layer 0.01 to 1 micron thick produced by vacuum condensation on said first silver halide layer of a mixture of silver halide with 10 to 20 mol percent of a sensitizing agent selected from the oxides, sulphides, selenides and tellurides of metals of Groups lb, 11b, and VIII of the periodic system.

4. A photographic material according to claim 3 in which the first layer is sensitized by a simultaneously condensed sensitizer selected from the halides and thincyanates of Cu Au Pt, Rh+, Fe, Ni, Co, Hg+, Pd, Sn, and Pb in a concentration between about 10- and 20 mol percent of the silver halide.

5. In the process of producing photographic images by imagewise exposing a light-sensitive silver halide layer to a high-intensity source of radiation to form an image which is most faintly visible and then developing said image by exposure of the layer to diffused light of lower intensity, the improvement which comprises using as the silver halide layer one that is from 1 to 100 microns thick produced by vacuum condensation on a support of a mixture of silver halide with from 10- to 20 mol percent of a sensitizing agent selected from the halides and thiocyanates of Cu+, Au+, Pt, Pd, Rh+, Fe, Ni, Co, Hg+, Sn and Pb.

6. A process for producing photographic silver images which comprises imagewise exposing a vacuum-condensed light-sensitive silver halide layer about 1 to microns thick and mixed with 10' to 20 mol precent of a sensitizing agent selected from the halides and thiocyanates of Cu+, Au Pt, Pd, R11 Fe, Ni, Co, Hg Sn, and Pb, and the oxides, sulfides, selenides and tellurides of metals of Groups 1b, 11b and VIII of the eriodic system to an object to be reproduced, developing said exposed material with a silver halide developing solution devoid of silver halide solvents to form a negative silver image, and transferring said image to an auxiliary support.

7. A process for producing photographic silver images which consists essentially of imagewise exposing a vacuum-condensed light-sensitive silver halide layer about 1 to 100 microns thick and mixed with 10- to 20 mol percent of a sensitizing agent selected from the halides and thiocyanates of Cu+, Au Pt Pd, Rh+, Fe, Ni, Co, Hg Sn, and Pb and the oxides, sulfides, selenides and tellurides of metals of Groups 1b, 11b and VIII of the periodic system, to an object to be reproduced developing said exposed material with a silver halide developing solution devoid of silver halide solvents to form a negative silver image, transferring said image to an auxiliary support, and then developing the residual silver halide of the photographic material to obtain therein a positive silver image of the object to be reproduced.

References Cited UNITED STATES PATENTS 2,500,421 3/1950 Land 9629 2,879,360 3/1959 Floyd 117106 3,219,451 11/1965 LuValle et a1. 96-94 3,319,450 11/1965 Goldberg 96108 3,219,452 11/1965 Hartouni 96-108 FOREIGN PATENTS 1,267,623 6/1961 France.

4/ 1939 Great Britain.

OTHER REFERENCES Abstract of Belgian Patent No. 598,861, June 1961, Derwent Belgian Patents Report, vol. 77A, July 7, 1961, p. A15. (96-67 Literature).

Clark, P. V. McD., et a1. Experiments on Photographic Sensitivity. J. Phot. Sci., vol. 4, 1956, pp. 1-20. (9694 BF) Glafkides, Pierre, Photographic Chemistry, London, Fountain Press, 1958, vol. 1 pp. -176. TR210.G.5.

Goldberg, G. M., et al. Investigations on Extending the Sensitivity Range of Single Crystalls and Evaporated Films of Silver Bromide, Aeron. Systems Division, Wright-Patterson Air Force Base, Ohio, August 1961. (9694 BE) 38, 41-43.

Hass, Georg. Preparation, Structure, and Applications of Thin films of Silicon Monoxide and Titanium Dioxide, 1. AM Ceramic Soc., vol. 33, No. 12, Dec. 1, 1950, pp. 353-360.

Goldberg, G. M. et a1. investigations on Extending the Sensitivity Range of Single Crystals and Evap. Films of AgBr. Aero. Syst. Div. Wright-Pat. A. F. Base, Ohio, Dec. 20, 1961, (96-94 BF) AD #264,061, pp. 11, 48.

NORMAN G. TORCHIN, Primary Examiner.

C. E. DAVIS, Assistant Examiner. 

5. IN THE PROCESS OF PRODUCING PHOTOGRAPHIC IMAGES BY IMAGEWISE EXPOSING A LIGHT-SENSITIVE SILVER HALIDE LAYER TO A HIGH-INTENSITY SOURCE OF RADIATION TO FORM AN IMAGE WHICH IS MOST FAINTLY VISIBLE AND THEN DEVELOPING SAID IMAGE BY EXPOSURE OF THE LAYER TO DIFFUSED LIGHT OF LOWER INTENSITY, THE IMPROVEMENT WHICH COMPRISES USING AS THE SILVER HALIDE LAYER ONE THAT IS FROM 1 TO 100 MICRONS THICK PRODUCED BY VACUUM CONDENSATION ON A SUPPORT OF A MIXTURE OF SILVER HALIDE WITH FROM 10**-2 TO 20 MOL PERCENT OF A SENSITIZING AGENT SELECTED FROM THE HALIDES AND THIOCYANATES OF CU+, AU+, PT+2, PD+2, RH+, FE+2, NI+2, CO+2, HG+, SN+2, AND PB+2.
 7. A PROCESS FOR PRODUCING PHOTOGRAPHIC SILVER IMAGES WHICH CONSISTS ESSENTIALLY OF IMAGEWISE EXPOSING A VACUUM-CONDENSED LIGHT-SENSITIVE SILVER HALIDE LAYER ABOUT 1 TO 100 MICRONS THICK AND MIXED WITH 10**-2 TO 20 MOL PERCENT OF A SENSITIZING AGENT SELECTED FROM THE HALIDES AND THIOCYANATES OF CU+, AU+ PT+2, PDQI, RH+, FE+2, NI+2, CO+2, HG+, SN+2, AND PB+2 AND THE OXIDES, SULFIDES, SELENIDES AND TELLURIDES OF METALS OF GROUPS IB, IIB, AND VIII OF THE PERIODIC SYSTEM, TO AN OBJECT TO BE REPRODUCED DEVELOPING SAID EXPOSED MATERIAL WITH A SILVER HALIDE DEVELOPING SOLUTION DEVOID OF SOLVER HALIDE SOLVENTS TO FORM A NEGATIVE SILVER IMAGE, TRANSFERRING SAID IMAGE TO AN AUXILLARY SUPPORT, AND THEN DEVELOPING THE RESIDUAL SILVER HALIDE OF THE PHOTOGRAPHIC MATERIAL TO OBTAIN THEREIN A POSITIVE SILVER IMAGE OF THE OBJECT TO BE REPRODUCED. 